Nature is a two column theme with a green header.
TheSpeedBlog is a fun two column WordPress theme with a widget enabled right-hand sidebar. Great for a motor racing fan of any kind.
Adsense theme is a widget ready theme filled with Adsense ads.
geepressed is a simple, green, two column Theme for WordPress 2.0/2.1.
Space Future is a search engine optimized two column theme.